Summary The Piper PA-31-350 (registration C-GVCP, serial number 317652080) was on a scheduled cargo flight from Nanaimo, British Columbia, to the civilian terminal on the south side of the military airbase at Comox, British Columbia. The crew members established communication with the Comox tower when they were at about 2000feet over Hornby Island, 12nautical miles southeast of Comox, and requested a practice back course/localizer approach to Runway30, circling for landing on Runway18. The request was approved and the aircraft continued inbound. When the aircraft was about two miles from the threshold of Runway30, the crew declared an emergency for an engine fire in the right engine. The tower alerted the airport response teams and requested standard data from the crew concerning the number of people and amount of fuel on board. Less than 30seconds after the crew first reported the emergency, the aircraft was engulfed in flames. Shortly thereafter, at 0741Pacific daylight time, the aircraft rolled inverted and struck the ground in a steep, nose-down, left-wing-low attitude. The aircraft broke apart and burned. Both crew members were fatally injured. Ce rapport est galement disponible en franais. Other Factual Information The weather at the time of the occurrence was reported as follows: wind 310True at 4knots; visibility 20statute miles; a few clouds at 25000feet. The incident occurred at 0741Pacific daylight time.1 Solidified droplets of molten aluminum and several small structural components were found along the inbound course for Runway30, as far back as 1000feet before the initial impact point. The aircraft's first contact with the ground was approximately 300feet short of the threshold for Runway30 and slightly right of the runway's extended centre line. The aircraft broke apart after the initial impact; the cockpit section was destroyed and both engines detached from the wings. The main wreckage was further damaged by a post-crash fire. The right engine, along with its cowlings and firewall, came to rest in an upright position a few feet aft of its normal station on the wing. Because of this separation, the right engine remained outside the area most affected by the post-crash fire. After a preliminary site survey, the wreckage was transported to the Transportation Safety Board (TSB) Regional Examination Facility for further examination. The engine cowls and wing surfaces were examined to identify in-flight burn patterns. Under normal circumstances the engine firewall, coupled with an exhaust heat shield assembly, located aft of the engine and below the wing, are intended to defend critical systems from heat. In this instance, an examination of the fire patterns revealed the following information: The gill cowl, inboard of the right engine, displayed a burn pattern that was likely caused in-flight. The leading edge of the right wing, just inboard of the right engine nacelle, burned through in flight. The main fuel tank, located immediately aft of the leading edge, had been penetrated by fire. Visual examination of the right-hand engine revealed that it had sustained moderate impact damage at the front. Most of the fire-damaged components and hoses were situated toward the rear of the engine. The fire originated near the centre of the accessory section, as evidenced by the heat or burn patterns in the area. A closer examination of the suspected area of fire origin revealed that the gasket material of the oil filter converter plate exhibited a bulging appearance and was partially extruded from beneath the converter plate. The oil filter was removed to gain access to the converter plate. During removal, it was noted that the oil filter gasket, which was subjected to a similar heat stress, was basically undamaged. The converter plate hold-down bolt required less than usual torque to remove. Once the plate was removed, it was evident that the converter plate gasket was extremely deteriorated (see Photo1). This deterioration would account for the reduced hold-down bolt torque. Right-engine converter plate gasket Because of the unrepresentative damage to the right-engine converter plate gasket, these components were removed from both the left and right engines and examined using Fourier Transform infrared spectroscopy. From that examination, the composition of the left-engine converter plate gasket was identified as an acrylonitrile-butadiene copolymer known as NBR or nitrile rubber. This gasket meets the standards of the appropriate Lycoming converter plate gasket (part number 06B23072). However, the deteriorated gasket taken from the right engine was found to be made of an ethylene-propylene-based elastomer known as EDPM or Dutral; this composition does not meet the standards of the current Lycoming component. Lycoming converter plate gaskets were originally identified by part number (P/N)LW-13388. Under normal circumstances, these gaskets would be replaced at engine overhaul or on-condition. However, on or after 01April1999, a bad batch of gaskets got into the aviation supply system; these gaskets were found to break down over time, allowing loss of engine oil. The problem was identified and first addressed by Lycoming Mandatory Service Bulletin543A, issued on 24July2000. Over the next three years, both Lycoming and the Federal Aviation Administration (FAA) continued to address the gasket issue using Airworthiness Directives (ADs), Supplements, Amendments and letters. A new gasket (P/N 06B23072) was subsequently manufactured to replace the old P/NLW-13388 gasket. The new gasket met all Textron Lycoming blueprint and test requirements and was installed on engines shipped from the factory after 04October2000. On 03 July 2002, the FAA issued AD 2002-12-07, which required, in part, that owners/operators of all affected engines replace the oil filter converter plate gasket with the newly manufactured part before 01October2003. An additional requirement of the ADwas that the converter plate be vibro-peened with the number "543"to provide a visual confirmation of ADcompliance. The accident engine had been overhauled at the Lycoming factory in1997, about two years prior to the bad gaskets entering the supply system. Its most recent annual inspection was done in the United States on 05March1999, after which it operated for about 19hours before being removed from service and placed in storage on 28June1999. There is no record of any maintenance action being done to this engine after the annual inspection of 05March1999, until Navair Charter purchased it and removed it from storage. As part of that activity, the maintenance personnel dismantled the engine and inspected, re-assembled and tested it prior to putting it back into operation on 14December2004 (log book entry date). The post-accident examination of the aircraft found that, in addition to containing an inappropriate gasket, the vibro-peening required by AD2002-12-07 was not present on the converter plate of the accident engine. Based on this data, it is evident that the requirements of the ADhad not been applied to this engine. It follows from the engine maintenance history that the defective gasket could have been put into the engine prior to its removal for storage, while it was in storage, or at some point after it was removed from storage and put back into operation by Navair Charter. Investigators conducted an informal telephone survey of supply and overhaul facilities, inspected eight affected engines and found the following: All surveyed aviation supply companies stocked only the new part-numbered gasket; the old part number has been cross-referenced to the new component. All stocked gaskets in supply at Nav Air Charter's facilities were the new components. Some overhaul companies reported that they are still finding and replacing the older style gaskets during engine repairs and overhauls. The instructions issued in AD2002-12-07 were not always carried out, in that some of the gaskets inspected by the TSB had not been glued and many of the converter plates had not been vibro-peened. A follow-on inspection of two additional engines found that, although both of the gaskets were made of the correct material, one of them was not stamped with the appropriate part number of the new component. Although this cannot be confirmed, it is possible that the unmarked gasket may be one of the original gaskets (PNLW-13388) that was installed prior to the introduction of the bad batch in1999. If that is the case, then AD2002-12-07 was not complied with on the inspected engine. The aircraft boost pumps are designed to remain ON during the operation of the aircraft. Additionally, emergency boost pumps are selected ON by the crew for both take-off and landing; this action ensures that pressurized fuel will reach the engine-driven fuel pump during the critical phases of flight. A firewall shut-off valve for each engine is available and may be selected by the crew for use in an emergency situation involving an engine fire. Activating this valve shuts off fuel to the engine. With the firewall shut-off valve closed, the boost pumps continue to operate, but the fuel is not fed to the engine driven pumps. The aircraft is not equipped with an engine fire-warning system, nor is such a system required by regulation. In the absence of a warning system, a pilot has to rely on other indications to determine whether a fire has ignited. These indications may include the following: visual identification of smoke or fire. In this instance there were no reports of trailing smoke prior to the aircraft being suddenly engulfed in flames; fluctuations of fuel or oil-pressure indications, or malfunctions of the propeller pitch controls; and/or degraded engine performance or yaw in the direction of the failing engine. The aircraft is not equipped (nor required to be equipped) with an engine fire suppression system. Once the crew members identify the presence of a fire, they are trained to respond in accordance with a critical action checklist entitled "POWER PLANT FIRE IN FLIGHT." The first items in that check are to turn the firewall shut-off valve to OFF; close the throttle; feather the propeller; and place the mixture control to idle/cutoff. That sequence of actions is aimed at removing pressurized fuel and oil from the engine compartment, and shutting down and securing the affected engine. TSB inspectors found that the firewall shut-off valves for each of the two engines were in the OPEN positions. The physical positions of the valves and the position of the mechanical linkages to the cockpit control levers indicate that the crew had not activated the firewall shut-off system in response to the in-flight fire. The right propeller was subsequently disassembled for inspection and was found to be in the FINE PITCH position rather than FEATHER.